Regarding an electrophotographic image forming apparatus, the following configuration is proposed: a photoconductive drum, a developing roller, and the like as rotary members related to image formation are integrated as a cartridge that is attachable to and removable from a main body of the image forming apparatus (hereafter “apparatus main body”). To rotate the photoconductive drum in the cartridge, driving force is desirably transmitted to the photoconductive drum from the apparatus main body. A configuration of engaging a cartridge-side coupling member with an apparatus main body-side driving force transmitting unit, such as a drive pin, to transmit driving force is proposed.
In some image forming apparatuses, the cartridge is removable in a predetermined direction which crosses substantially perpendicularly a rotational axis of the photoconductive drum. An apparatus main body which does not have a mechanism for moving the drive pin of the apparatus main body in the direction of the rotational axis by opening and closing a cover of the apparatus main body is proposed. Specifically, PTL 1 and PTL 2 disclose configurations in which a coupling member provided at an end of a photoconductive drum can be tilted to the rotational axis of the photoconductive drum. The coupling member provided in the cartridge engages with a drive pin provided in the apparatus main body so that driving force is transmitted to the cartridge from the apparatus main body.